How to obfuscate an Android library (.jar file) using Proguard in Eclipse

as suggested in the comments to one of the answers above (but which i didn’t notice at first because it was buried amongst one of the “additional comments”) …

we simply run progruard on the command line (see the first block below) on the library outside of eclipse with the parameters in the second block below in our our proguard.cfg file (and definitely do not use -dontpreverify, or projects that use your project as an android library won’t be able to properly be obfuscated due to StackMapTable problems from your project.jar).

command line:

$ java -jar $ANDROID_SDK/tools/proguard/lib/proguard.jar \
  -libraryjars $ANDROID_SDK/platforms/android-18/android.jar @proguard.cfg
  -outjars /tmp/project.jar -verbose

proguard.cfg:

-optimizationpasses 5
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontwarn our.company.project.R*
-injars bin/project.jar
-verbose
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*

-keep class org.apache.3rdparty.stuff.**
-keep public class our.company.project.ProjectAPI
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference

-keepclassmembers public class our.company.project.ProjectAPI {
    public static <fields>;
}

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers class * extends android.app.Activity {
    public void *(android.view.View);
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
    public static final android.os.Parcelable$Creator *;
}

it’s possible not all of the parameters and -keep items are strictly necessary (other than not using -dontpreverify as previously mentioned), but most of these make sense to me as items that need to be there if you have an Activity class extension in the library you are exporting.